Some effects of the moisture distribution in the subcloud layer on the thermal structure of a mature severe thunderstorm

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Lin, Y. J. ; Hwang, H. J. (2011)

A four-layer, non-entraining axial-symmetric, steady-state model of a severe thunderstorm with a rotating updraft is used to study some effects of the low-level moisture fields on the thermal and dynamical structure of the storm. This model represents the third in a series of three models which have been produced at Saint Louis University. It differs from the other two which were developed by Lin & Martin (1971, 1972) by the fact that moisture becomes a specified input parameter rather than a deduced one. The three models have been checked to assure their internal consistency so that any one of them can be used to generate a common field of gridded variables depending upon the nature of the observed evidence at hand. The selective mix of observed and generated data within the updraft of the modelled storm, provided by the particular model of this respect, was used to evaluate (1) vertical velocities from the mass continuity equation, (2) moisture distribution in the subcloud layer from the continuity equation for water vapor, (3) the field of pressure based on the radial equation of motion, (4) the temperature field using the thermodynamic energy equation, and (5) moisture fluxes, latent heat releases and static energies utilizing the data obtained from (1) through (4). The results indicate that a substantial percentage of the latent beat releases within a storm must be confined to the lower portion of the atmosphere in order for a warm-core center to be maintained. The low-level relative humidity of the embedding environment was found to be a strong indicator of severe thunderstorm development. The “static energy differentials” between a storm and its environment are compared for a modelled and observed storm to illustrate certain agreements among the modelled and natural physical processes in operation.DOI: 10.1111/j.2153-3490.1974.tb01632.x
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